How do I make custom movesets for specific characters? and is there a tutorial? (Without easy custom movesets)

[axolo6]

I want to make a character moveset for 3 different characters:
_A Mist beam (like Bowser but with mist particles) by pressing L
_A Dash that only works while walking by pressing L
_ A change in size where he can become smaller by pressing L
If someone can show me how to do it or show me a tutorial I would be very Grateful (please it's been two weeks since I started searching)